Arthropod repellency, especially tick (Ixodes ricinus), exerted by extract from Artemisia abrotanum and essential oil from flowers of Dianthus caryophyllum.

A toluene extract of southernwood (Artemisia abrotanum) and the essential oil from flowers of carnation (Dianthus caryophyllum ) exerted pronounced a repellent effect both against ticks (nymphs of Ixodes ricinus) and yellow fever mosquitoes (Aedes aegypti). The most potent repellents found were coumarin and thujyl alcohol from A. abrotanum and phenylethanol from D. caryophyllum where coumarin and thujyl alcohol were also detected.

Repelling properties of some plant materials on the tick Ixodes ricinus L.

The repellent effects on nymphal stages of Ixodes ricinus L. of some plant materials have been studied in the laboratory. The plant material consisted of an ethanolic extract from Achillea millefolium L., and volatile oils of birch and/or pine tar, citronella, cloves, eucalyptus, geranium, lavender, lily of the valley and peppermint. The most pronounced effects were observed for the oils of citronella, cloves and lily of the valley. They possessed repelling activities of the same magnitude as the reference repellent DEET (N,N-diethyl-m-toluamide). Some major constituents of these oils, e.g. citronellol and geraniol (oil of citronella and lily of the valley) and eugenol (oil of cloves) showed pronounced repelling effects. This was also the case for phenethyl alcohol, a minor component in the oil from lily of the valley.

Efficacy of plant extracts and oils as mosquito repellents.

Some natural products, extract of Achillea millefolium (yarrow), birch/pine tar-, citronella-, clove-, eucalyptus-, geranium-, lavender-, lily of the valley- and peppermint oils have been tested for repellency in the laboratory against Aedes aegypti and in the field predominantly against Aedes communis and A. cinereus. The laboratory tests showed that yarrow extract exhibited a similar repellency as the reference substances N,N-diethyl-m-toluamide and N,N-diethyl-mandelic acid amide. A good repelling effect was also obtained with the oils of birch/pine tar and eucalyptus. The field tests revealed that the extracts and oils with good activity against Aedes aegypti also were effective against A. communis and A. cinereus. Furthermore oils of citronella and lily of the valley showed similar activity and were comparable with the used reference substances mentioned. Each of these natural products contained a great number of constituents when characterized by chromatography/mass spectrometry. Available data in the literature were gathered, both regarding mosquito repellency and toxicity for humans and larger animals, for each product as well as its major constituents.

Ortho hydroxy-substituted molecules might be of importance for the prevention of bloodsucking by mosquitoes.

Achillea millefolium extract contains several compounds, which prevent Aedes aegypti from feeding blood. Some of these compounds might interfere with each other. Caffeic acid, mandelonitrile glucoside, pyrocatechol, salicylic acid, and stachydrine were chosen for tests in paired mixtures. The effects were mainly antagonistic or additive. Exceptions were the mixtures of mandelonitrile glucoside and pyrocatechol, and possibly stachydrine and pyrocatechol where slight synergistic effects could be demonstrated. In connection with these studies the question arose if ortho substituents, especially free hydroxy groups, might be of importance for the effect on mosquitoes. It was shown that in the test series pyrocatechol (ortho-substituted), resorcinol (meta-substituted) and hydroquinone (para-substituted), pyrocatechol showed the highest activity. Furthermore, the importance of the free ortho hydroxy groups in the molecule was indicated by a decreased activity by the mono- and di-methylation of the hydroxy groups in pyrocatechol, i.e. the compounds guaiacol and veratrol.

Evaluation of anti-inflammatory activity of some Swedish medicinal plants. Inhibition of prostaglandin biosynthesis and PAF-induced exocytosis.

Plants used in Swedish traditional medicine to treat inflammatory diseases and/or wounds were selected, based on literature data, for evaluation of inhibitory activity on prostaglandin biosynthesis and platelet activating factor (PAF)-induced exocytosis in vitro. Fifty-nine water extracts from 52 different plants in 28 families were tested. A number of plants, e.g. Calluna vulgaris, Corylus avellana, Geum urbanum, Juniperus communis, Polygonum aviculare, Potentilla erecta and Salix caprea were found to be active in both assays. The most potent cyclooxygenase inhibitors were extracts of Calluna vulgaris, Potentilla erecta and Salix caprea. None of the extracts inhibited just the prostaglandin biosynthesis. In the PAF-test, high inhibition was obtained by 19 extracts, the most potent of which were from Geum rivale, G. urbanum, Solanum dulcamara, Symphytum x uplandicum and Vaccinium vitis-idaea. The in vitro effects in relation to the traditional use, chemical contents and botanical classification, as well as the possibilities and the limitations of the methods are discussed.

Anti-inflammatory studies on Menyanthes trifoliata related to the effect shown against renal failure in rats.

Menyanthes trifoliata L. is used in Swedish traditional medicine for the treatment of inflammatory diseases of the kidney, e.g. glomerulonephritis. Earlier studies have shown that MtL increases glomerular filtration rate after renal reperfusion ischemia. This activity was suggested to be PAF-inhibitory since MtL also inhibited PAF-induced exocytosis in vitro on human neutrophils (IC(50) = 0.16 mg/ml). The present study further characterizes the anti-inflammatory properties of a rhizome decoction of this plant. MtL inhibited carrageenan-induced rat paw edema (ID(50) ≈ 1.7 g/kg p.o.) and ethyl phenylpropiolate-induced rat ear edema (32% at 2.0 g/kg p.o.) in a dose-dependent manner. Further studies revealed that MtL inhibited both fMLP-induced exocytosis (IC(50) = 0.16 mg/ml) and elastase activity (IC(50) = 0.16 mg/ml). According to these results it is likely that the activity shown in the PAF-test is at least partly due to an inhibition of elastase. MtL showed only minor hemolytic properties at the concentrations used in the PAF- and fMLP-tests, suggesting that the cells in these tests are undamaged. The decoction also inhibited the biosynthesis of LTB(4) (IC(50) ≈ 0.73 mg/ml) and prostaglandins (IC(50) = 0.37 mg/ml) in vitro in a concentration-dependent way. However, at concentrations where the decoction is active in the LTB(4)-test, it also possesses hemolytic properties.

The effect of Menyanthes trifoliata L. on acute renal failure might be due to PAF-inhibition.

The influence of oral administration of a water decoction made from the rhizomes of Menyanthes trifoliata L. (MtL) was studied in rats, before and after exposure of 45 min of renal ischemia. Under normal conditions (preischemia) MtL treated kidneys behave similarly to untreated kidneys, measured as glomerular filtration rate (GFR), urine flow and the ability of the kidneys to concentrate urine. After ischemia, the MtL animals, showed much more preserved renal function, demonstrating a glomerular filtration rate (GFR) that was more than 3 times higher than in untreated animals. An in vitro model of platelet activating factor (PAF)-induced exocytosis in human neutrophils, was used to investigate PAF-inhibiting activity of MtL. The standard PAF antagonists WEB 2086, WEB 2170 and SRI 63-441 were used and compared to MtL. All PAF antagonists showed a concentration-dependent inhibition of the exocytosis of activated neutrophils, the PAF-inhibitor WEB 2170 being the most potent, with an IC(50) = 0.2 µg/ml while MtL showed an IC(50) = 160 µg/ml. It is concluded that the higher GFR seen after acute renal failure and treatment with MtL, could, in part, be due to a PAF-antagonistic effect.